Continuation of research on specific, long-range problems of intensity effects and processing in the auditory and tactile systems. The research has generated hypotheses and broad generalizations that require further testing. It has also produced substantial empirical information that requires further interpretation and integration. These results make additional experimentation and theoretical work necessary. A multidisciplinary approach is being used, including 1) human behavior, 2)neurophysiology, and 3) neuroanatomy, with the specific goal of providing definitive answers to still unresolved problems of transduction and intensity coding in the two sensory systems. Specific experiments within modalities run parallel and complementary courses; the six projects are interlocked in their goals. A systems-analysis approach will be used. Gloabla functions are determined from human psychophysics. Experiments focus on stimulus intensity, frequency and time parameters of intensity discrimination and on intensity effects in the discrimination of complex stimuli, and the correlation of behavioral and neural responses within the auditory system. Contributions of relevant components of the system to global functions are sought through direct physiological and morphological experiments. We will see to psychophysically explore the parameters of intensity discrimination in human tactile systems with the goal of relating global functions to the underlying physiological mechanisms and their morphological substrates. Some experiments concern the effects of stimulus intensity on the neural responses in the auditory periphery. Other experiments are focused on the effects of stimulus intensity upon neuron responses in the tactile periphery so that these may be related to sensory functions and morphology. There will be focus on the roles in transduction and intensity effects played by auditory hair cells, eighth nerve and cochlear nucleus, and correlates to components of the peripheral tactile system. We will also focus on receptor and fiber types in the peripheral tactile systems and attempts to elucidate their roles in transduction and intensity effects. Experiments involve humans as well as other vertebrate animals. All experiments are consistent with the expertise of a multidisciplinary team, and long-range goals of fundamental importance to understanding human perception and its underlying neural mechanisms. the information generated relates closely to the practical needs of the biomedical community.